1. Field of the Invention
The present invention is a process for preparing organofunctional organosilicon compounds by reacting olefins with a compound containing H—Si groups in the presence of a dissolved platinum catalyst and at least one further additive component.
2. Discussion of the Background
Organofunctional silanes are of great economic interest and are now employed in many industrial applications. 3-Chloropropylchlorosilanes in particular are important intermediates in the preparation of organofunctional silanes. They are generally prepared by the hydrosilylation of allyl chloride. For example, 3-chloropropyltrichlorosilane and 3-chloropropylmethyldichlorosilane can be used to prepare, for example, 3-chloropropyltrialkoxysilanes, 3-chloropropylmethyldialkoxysilanes, 3-aminopropyltrialkoxysilanes, 3-aminopropylmethyldialkoxysilanes, N-aminoethyl-3-aminopropyltrialkoxysilanes, N-aminoethyl-3-aminopropylmethyldialkoxysilanes, 3-cyanopropylalkoxysilanes, 3-glycidyloxypropylalkoxysilanes, 3-methacryloxypropylalkoxysilanes, to name only a few examples.
The addition of Si—H groups onto aliphatic multiple bonds has been known for a long time, and is known as hydrosilylation. This reaction is promoted by, for example, homogeneous and heterogeneous platinum catalysts. Examples of heterogeneous platinum catalysts include, for example, platinum metal, in particular finely divided platinum on a support such as activated carbon. Homogeneous platinum catalysts include, for example, hexachloroplatinic acid, alcohol-modified hexachloroplatinic acid, olefin complexes of hexachloroplatinic acid or vinylsiloxane complexes of hexachloroplatinic acid or of platinum. Complexing reagents are frequently added to a catalyst system to increase selectivity and reactivity, which in some cases also improves the solubility of the platinum compound.
EP 0 573 282 A1 discloses the use of H2PtCl6 in 2-ethylhexanal and also addition of m-xylene hexafluoride.
EP 0 263 673 A2 teaches the preparation of 3-chloropropyltrichlorosilane by hydrosilylation using hexachloroplatinic acid dissolved in isopropanol (Speier catalyst), and the addition of N,N-dimethylacetamide.
The hydrosilylation of allyl chloride and methyldichlorosilane in the presence of the Speier catalyst system generally forms two undesirable by-products: chloropropylmethylchloropropoxysilane and dichloromethylpropoxysilane. Chloropropylmethylchloropropoxysilane can be separated from the target product chloropropylmethyldichlorosilane (CPMDCS) only with great difficulty.
There are many examples of metal complex catalysts added to reactions for the purpose of positively influencing homogeneously catalyzed reactions.
Karstedt catalysts (Pt(0) complexes) have also been used for hydrosilylations since 1973. Thus, for example, DE-A 19 41 411 and U.S. Pat. No. 3,775,452 disclose platinum catalysts of the Karstedt type. This type of catalyst generally has a high stability, especially in an oxidizing matrix, a high effectiveness and a low tendency to isomerize carbon frameworks.
EP 0 838 467 A1 discloses a process for preparing silanes having fluoroalkyl groups using a Pt(0) complex catalyst which is dissolved in xylene.
Experiments show that the hydrosilylation of, for example, allyl chloride with methyldichlorosilane at a molar ratio of 1:1 in the presence of a Karstedt catalyst such as CPC072® gives a yield of 3-chloropropylmethyldichlorosilane of not more than 49 mol %.